Performance of bio-asphalts: state of the art review

The global population spike, rise in industrialization, and highway infrastructure development induce focus on sustainable development. The ever-increasing consumption of non-renewable crude oil and asphalt levies a heavy toll on economic welfare of future generations. This enormous demand of asphalt is due to its wide applicability in flexible pavements. Therefore, the construction industry is exploring the partial substitution of renewable materials in asphalt with a focus on economical, social, and environmental benefits. The current decade has seen a rampant rise of bio-asphalt as an alternative to asphalt. Hence, it is imperative to explore the performance of bio-asphalt for its sustainable applicability. This review comprehensively summarizes the performance of bio-asphalt obtained from various biomass sources. It deals with elemental composition of bio-oil, preparation procedure, rheological performance, mixture performance, and aging mechanism of bio-asphalt along with modification required to improve the performance. The environmental impacts and field application of the bio-asphalts are also discussed.

Effects of pyrolysis parameters on physicochemical properties of biochar and bio-oil and application in asphalt

Adoption of renewable energy sources such as biomass has been increasing worldwide. In this study, fast pyrolysis as an acceptable and viable method to get renewable bio-oil and biochar is used. Different temperatures and N₂ flow velocities were used in the fast pyrolysis process to evaluate the pyrolysis yield of biochar and bio-oil. The waste wood and pig manure were utilized to prepare biochar and bio-oil. X-ray fluorescence, X-ray diffraction, high-pressure liquid chromatograph, Micro confocal laser Raman spectrometer, Fourier transform infrared spectrometer, and dynamic shear rheometer were used to measure the chemical compositions, structure, and pyrolysis yield of biochar and bio-oil. The obtained results indicate that pyrolysis temperature increases the purity of inorganic oxide in biochar and N₂ flow velocity promotes the yield of carbon in biochar. The increase of N₂ flow velocity would increase the acid property of bio-oil and damage the products yield of bio-oil. It was also observed that biochar could remarkably alter the fundamental performances of petroleum asphalt including penetration, softening point, ductility, viscosity, and complex modulus. The most important is that the upgraded bio-oil can be used to replace partly or fully the petroleum asphalt which is a promising biomass application.

Flow-induced crystallization of biochar in bio-asphalt under various aging conditions

Flow-induced crystallization (FIC) in polymers is an important problem that occurs on a very rapid time scale. This study aims to evaluate the flow-induced crystallization of bio-asphalt modified with different contents of biochar under various aging conditions. Small angle X-ray scattering and molecular dynamic simulations were performed to impose extensional deformation and the nucleation process. The rheological properties were measured using the dynamic shear rheometer (DSR) and the morphology of biochar modified bio-asphalt (BMBA) was measured using an optical microscope. The relative scattering intensity during crystallization appeared to peak at four strain rates: 13.2 s^-1, 19.6 s^-1, 25.4 s^-1, and 27.3 s^-1. The results showed that the addition of biochar could improve the flow-induced crystallization and enhance the high-temperature properties of bio-asphalt. Moreover, crystallization status of BMBA is lamellar crystals. Ultraviolet and pressure aging vessel aging could remarkably affect the crystallization status of BMBA and promote the formation of crystals.